THIS INFORMATION IS HERE TO HELP YOU GET UP TO SPEED IN AN AREA YOU MAY NOT HAVE PREVIOUS EXPERIENCE, AND GIVE YOU SUPPORT IN YOUR PREPRODUCTION PREPARATIONS. WEATHER PERMITTING, MOST UNDERWATER SHOOTS RUN VERY SMOOTHLY AND ARE OFTEN GREAT FUN.
COMMERCIAL DIVING AND THE LAW
If in doubt see the HSE DIVING WEBSITE. It is very important to be aware that any diving activity taking place in UK waters, for commercial reasons, is covered by UK Law. This means that even if you are employing an individual to weld your oil-rig or asking him to jump in the water to "grab a few shots" for your TV programme, the employer would be answerable in a UK court if there was ever an accident! It is therefore imperative for any production company to employ diving staff who hold safety tickets issued by the UK Health and Safety Executive.
Gavin Turnbull and all his diving team hold these certificates, as well as similar certificates associated with diving boats operating off-shore. Outside UK waters the situation is a little vague; however, for example, the BBC will not employ divers without UK HSE tickets for underwater filming abroad. For most insurance purposes, CMAS 3* certificates, such as PADI (Professional Association of Diving Instructors) "Divemaster" will be acceptable in case of accident, but only outside UK waters. However, no matter where we are diving, we will always continue to work within the guidelines as set out by the UK Health and Safety Executive. It is highly unlikely that you, as potential employers, based in the UK or abroad, will be seen as negligent in a UK Court of Law, so long as you employed HSE registered divers and followed the recommendations of the dive supervisor.
CINEMATOGRAPHY AND FILMING UNDERWATER
Depth, Colour and Vis ("Visibility") Do we need lights? As "natural" light travels underwater it is heavily filtered. The red side of the spectrum disappears first which is why blue is such a predominant colour underwater. For a camera to "see" good colour underwater there are two ways to help the process. Firstly filtering. With all that red being filtered out you can put an equivalent "red" filter over the camera lens. This will help to correct the colours, but the deeper you go the stronger the filter you will need. Unfortunately the deeper you go the less available light there is so eventually it will become too dark too film!
At this point, lighting might be the answer. To bring lighting underwater only solves the problem if the subject is within range of the lights themselves. Beyond that range the pictures will be more blue than if they weren't even filtered! Water visibility is crucial in this part of planning. One could dive in 50 meters of crystal clear water without lights but in very "soup-like" visibility in 1 or 2 meters lighting may be required.
Lighting is always a last resort and must be budgeted only if necessary. With the new Digital Betacam and HD-Cam systems much of the filtering can be done "digitally" offering better colour quality at deeper depths.
TIDES FOR DIVING & BOAT LAUNCHING
Tides have 2 main factors on dive planning...... firstly depth; do we want to dive at low tide or high tide? It is not uncommon to have a low-to-high tide difference of 4 to 6 meters. That makes has a big significance to the dive times illustrated above. Perhaps a 15 meter dive could be a 9 meter dive at low tide or a 6 meter high tide dive could be a bit of a headache at low tide! Often boats cannot be launched at low tide. To find out about suitable launching site in the UK visit the BOAT LAUNCH UK website.
The other factor is current. An hour either side of low or high tide is known as "slack water". This is when the tidal current has stopped moving and the current offers little or no resistance to the diver so he can swim around without getting tired. The time difference between "high" and "low" water is usually just over 6 hours allowing for 2 tides (high and low) per day. As the moon rises approximately one hour later every day therefore the tide times are always an hour or so later than the previous day.
WEATHER
The weather can prove to be a major headache when planning for a filming dive. Try using the BBC WEATHER page for a 5 day forecast to plan ahead. We understand that you as well as we have all sorts of commitments, not only in time but in budget. It is safer to plan an extra day or so in case the weather dictates. Ultimately it is down to the dive supervisor as to whether diving is safe enough to take place. We offer a 50% "stand-by rate" should weather be a problem.
HOW MANY DIVES?
It is possible to make 3 or even 4 dives in a day but the above times are greatly reduced, after subsequent dives, depending on the time spent above water between repetitive dives. The shallower...... the more work done!!
TIME AND DEPTH
In case you are not familiar with SCUBA diving, please bear the following points in mind. As a diver descends, the water pressure increases and therefore, to fill his lungs, the diver needs to breathe air at an equivalent "increased" pressure. This means that the air entering the divers blood stream is far more concentrated than at the surface. As the time and depth (ie pressure) increases the more the"pressurised" air is stored in the body. At a certain point, if the diver should make a "quick" return to the surface, this stored and highly pressurised air would suddenly expand into bubbles in the blood-stream and cause bubbles to be trapped in the body's tissue or muscle. This is known as decompression sickness or "the bends". It is important to remember that the first 10 meters of descent are the most dangerous, as pressure doubles in relation to surface air pressure (at sea level).
To avoid decompression sickness we always use dive "tables" which tell us the maximum time at a given depth before a gentle accent (18 metres per minute) will diffuse any "trapped air" in a safe manner. To overshoot these guide-lines means we would then be entering a form of diving known as saturation diving which means direct access to the surface is suddenly denied and "decompression" stops have to be made. We avoid this kind of diving at all costs except in emergency situations. All our divers carry computers to enable them to re-evaluate time and depth situations. We will never allow a dive plan to enter into a saturation situation except in emergency.
As a general rule time and depth guidelines are as follows;
9.0 meters = 163 minutes
12.0 meters = 89 minutes
15.0 meters = 57 minutes
18.0 meters = 39 minutes
21.0 meters = 29 minutes
24.0 meters = 24 minutes
27.0 meters = 18 minutes
30.0 meters = 14 minutes
UNDERWATER COMMUNICATIONS
The secret to successful underwater filming is good communications. Standard SCUBA equipment involves breathing on a regulator mouthpiece which makes speech impossible. Our divers are trained to use a special face mask with a built in microphone which allows the diver to speak to the surface (dive supervisor and director) using radio transmission or to other divers in the water. Usually the cameraman, assistant and dive supervisor will all have 2 way communications, but it is possible to attach receiver only units to untrained divers (eg actors or presenters). All our staff are equipped with diver communications included in the quoted prices, but for a small extra charge we can provide other divers with "receive only" units which are attached to standard SCUBA diving masks. Also with certain cameras we can provide an underwater image to a portable monitor on the surface.
TEAM WORK
To comply with UK Health and Safety Executive guidelines it is important to budget for the correct members of a diving team. If you want to film in a swimming pool or confined water area you need to employ a dive supervisor as well as an underwater cameraman. To dive in open water you will need to budget for the cameraman, the supervisor and an assistant who will double as safety diver to accompany the cameraman. A supervisor is required for all diving operations but will usually not enter the water. However, he will be kitted up on "stand-by" in case of emergency. It is also a guideline by the HSE for boat diving to have a second person on stand-by with the supervisor to assist an injured diver back on to the boat. This could be an able bodied member of the production team but if in doubt, budget for an extra team member who is an HSE diver and trained in CPR first aid. It is also VITAL to be aware that in UK waters the above guide-lines are for the Health and Safety of the diving camera crew only and that any other personnel diving (eg. in-front of the camera) will require their own safety crew. We can also arrange this for you.
DIVING ABROAD
If you want to film abroad it is usually advisable to find a dive centre in the area you wish to film in. They can provide useful local knowledge and facilities (such as boats, weight-belts, personnel and compressed air supply) in many different countries around the word. Try searching the PADI (Professional Association of Diving Instructors) data-base. Everything else we can provide and have flown out.
